WO2015076232A1

WO2015076232A1 - Cutting insert, cutting tool, and method for producing cut article

Info

Publication number: WO2015076232A1
Application number: PCT/JP2014/080425
Authority: WO
Inventors: 寛久石
Original assignee: 京セラ株式会社
Priority date: 2013-11-20
Filing date: 2014-11-18
Publication date: 2015-05-28
Also published as: US10058935B2; EP3072618B1; EP3072618A1; EP3072618A4; JP6228229B2; US10406610B2; US20160288223A1; US20180193929A1; JPWO2015076232A1

Abstract

A cutting insert (1) according to one embodiment is equipped with a bottom surface (2), a top surface (3), a lateral surface (4) provided between the bottom surface (2) and the top surface (3), a pair of corner cutting blades (5) positioned at the intersection of the top surface (3) and the lateral surface (4), and a principal cutting blade (6) positioned between the pair of corner cutting blades (5). When seen from a lateral-surface view, the principal cutting blade (6) has a downwardly recessing curved section (61) and a pair of straight sections (62) extending from the curved section (61) toward the pair of corner cutting blades (5). When seen from a lateral-surface view, a section (6p) positioned lowest in the curved section (61) is nearer one (5b) of the corner cutting blades than the other.

Description

Cutting insert, cutting tool, and manufacturing method of cut workpiece

This aspect relates to a cutting insert, a cutting tool, and a manufacturing method of a cut workpiece.

Conventionally, cutting inserts described in Japanese Patent Application Laid-Open No. 9-216113 (Patent Document 1) and Japanese Patent Application Laid-Open No. 11-347826 (Patent Document 2) are known as cutting inserts used for cutting work materials. Yes. Specifically, the cutting inserts described in

Patent Documents

1 and 2 are used for a rolling process such as face milling or end milling. The cutting inserts described in

Patent Documents

1 and 2 are curved so that the cutting edge is recessed downward in a side view.

The cutting inserts described in

Patent Documents

1 and 2 are set such that the cutting angle of the main cutting edge is 45 ° or 90 ° with respect to the work material. For this reason, when cutting the work material, the thickness of the chip increases, and as a result, the impact applied to the main cutting edge is large. Furthermore, there is a high possibility that a large amount of heat is generated when the main cutting edge cuts the workpiece, and the main cutting edge is chipped.

A cutting insert according to one aspect of the present aspect includes a polygonal upper surface having a pair of corner portions and a side portion located between the pair of corner portions, a polygonal lower surface corresponding to the upper surface, the lower surface, A side face provided between the upper surfaces, a pair of corner cutting edges located at the intersection of the pair of corners and the side faces on the upper face, and a main cutting edge located between the pair of corner cutting edges The main cutting edge has a concave shape recessed downward as a whole, and has a concave curved first portion recessed downward as viewed from the side, and the pair of corners from the first portion. A pair of linear second portions that extend toward each of the cutting blades and increase in height as approaching the pair of corner cutting blades, and the lowermost portion of the first portion is a side surface Looking toward one of the corner cutting edges It is characterized in that.

It is a perspective view which shows the cutting insert of one Embodiment. It is a top view of the cutting insert shown in FIG. It is a side view of the cutting insert shown in FIG. It is a perspective view which shows the cutting tool of one Embodiment. It is a side view of the cutting tool shown in FIG. It is the side view to which the attachment state of the cutting insert which is a part of cutting tool shown in FIG. 5 was expanded. It is the side view to which the main cutting edge of the cutting insert shown in FIG. 6 was expanded. It is a perspective view which shows 1 process of the manufacturing method of the cut workpiece of one Embodiment. It is a perspective view which shows 1 process of the manufacturing method of the cut workpiece of one Embodiment. It is a perspective view which shows 1 process of the manufacturing method of the cut workpiece of one Embodiment.

<Cutting insert>
Hereinafter, a cutting insert 1 (hereinafter also simply referred to as an insert 1) according to an embodiment will be described with reference to FIGS. The two-dot chain line in FIG. 1 indicates the central axis X of the cutting insert 1.

As shown in FIGS. 1 to 3, the insert 1 of the present embodiment includes a lower surface 2, an upper surface 3, a side surface 4 provided between the lower surface 2 and the upper surface 3, and an intersection line between the upper surface 3 and the side surface 4. A pair of corner cutting edges 5 (5a, 5b) and a main cutting edge 6 positioned between the pair of corner cutting edges 5 (5a, 5b). The upper surface 3 has a polygonal shape and includes a pair of corner portions and a side portion located between the pair of corner portions. The lower surface 2 has a polygonal shape corresponding to the upper surface 3. The pair of corner cutting edges 5 are located at the intersection of the pair of corners and the side surface 4 on the upper surface 3. The main cutting edge 6 is located at the intersection of the side surface 4 and the side surface 4 on the upper surface 3.

The main cutting edge 6 has a concave shape that is recessed downward as a whole, and has a first part (curved part) and a pair of second parts (straight part). The first portion has a concave curve shape that is recessed downward as viewed from the side. The pair of second portions has a linear shape, extends from the first portion toward each of the pair of corner cutting edges 5 (5a, 5b), and approaches the pair of corner cutting edges 5 (5a, 5b). According to the height is high. And the part (bottom part) 6p located in the lowest part in the 1st site | part has approached the side of one corner cutting blade 5b in side view.

Of the pair of

corner cutting edges

5a and 5b, the one close to the processing surface of the work material when cutting the work material is the first corner cutting edge 5a, and the work material is processed when cutting the work material. The one located away from the surface is the second corner cutting edge 5b.

The upper surface 3 has a polygonal shape and includes a pair of corner portions and a side portion located between the pair of corner portions. The lower surface 2 has a polygonal shape corresponding to the upper surface 3. The lower surface 2 and the upper surface 3 of the insert 1 in this embodiment are each a quadrangular shape having a plurality of corners. The corner portion in the present embodiment is not a corner in a strict sense, but an arc shape that is curved when viewed from above.

Therefore, in the insert 1 of the present embodiment, the arc-shaped portion positioned at the corner of the upper surface 3 becomes the corner cutting edge 5, and the portion positioned between the arc-shaped corners on the periphery of the upper surface 3 is the side portion. Thus, the main cutting edge 6 is obtained.

The insert 1 has a through-hole H penetrating vertically. The through hole H is formed from the central portion of the upper surface 3 to the central portion of the lower surface 2. The through hole H is a hole through which a screw is passed, and is used to fix the insert 1 to the holder by screwing the screw to the holder. The opening of the through hole H is circular when viewed from above, and has a diameter of 2 to 12 mm, for example. Since the through hole H is formed from the center of the upper surface 3 to the center of the lower surface 2, the central axis X of the through hole H extends in the vertical direction.

The material of the insert 1 is, for example, cemented carbide or cermet. The composition of the cemented carbide is, for example, WC—Co produced by adding cobalt (Co) powder to tungsten carbide (WC) and sintering, and WC—coating WC—Co with titanium carbide (TiC). There is WC—TiC—TaC—Co in which tantalum carbide (TaC) is added to TiC—Co or WC—TiC—Co. The cermet is a sintered composite material in which a metal is combined with a ceramic component, and specifically includes a titanium compound mainly composed of titanium carbide (TiC) or titanium nitride (TiN).

The surface of the insert 1 may be coated with a film using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. Examples of the composition of the coating include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al ₂ O ₃ ).

The maximum width of the lower surface 2 or the upper surface 3 of the insert 1 is 5 to 20 mm. The height from the lower surface 2 to the upper surface 3 is 2 to 8 mm. The shapes of the upper surface 3 and the lower surface 2 are not limited to the above-described form. For example, the shape of the upper surface 3 when viewed from above may be a polygonal shape such as a triangle, pentagon, hexagon, or octagon.

The upper surface 3 has a land surface 31 and a rake surface 32 as shown in FIGS. The land surface 31 is continuous with the corner cutting edge 5 and the main cutting edge 6. The corner cutting edge 5 and the main cutting edge 6 correspond to the outer edge of the upper surface 3. The rake face 32 is provided in a region closer to the through hole H than the land face 31. The rake face 32 is an inclined surface whose height decreases as it goes toward the through hole H. Note that the lower surface 2 in the present embodiment is formed on a plane orthogonal to the central axis X.

The land surface 31 is continuous with the corner cutting edge 5 and the main cutting edge 6, and is provided in a region closer to the central axis X than the corner cutting edge 5 and the main cutting edge 6. The land surface 31 is a band-like surface having a narrow width provided along the corner cutting edge 5 and the main cutting edge 6, and an inner angle formed with the side surface 4 is larger than the rake surface 32. Specifically, the land surface 31 is an inclined surface that is substantially parallel to the lower surface 2 or increases in height toward the center. In addition, the land surface 31 may have a height that decreases in a part of a region near the corner cutting edge 5 toward the center.

A corner cutting edge 5 and a main cutting edge 6 are formed at the intersection of the land surface 31 and the side surface 4. The land surface 31 is provided to increase the strength of the corner cutting edge 5 and the main cutting edge 6. The rake face 32 located inside the land surface 31 is an inclined surface whose height decreases toward the center. Therefore, the internal angle formed by the rake face 32 and the side face 4 is small.

However, since the internal angle formed by the land surface 31 and the side surface 4 is larger than the internal angle formed by the rake surface 32 and the side surface 4, the strength of the corner cutting edge 5 and the main cutting edge 6 is increased by having the land surface 31. be able to. The width of the land surface 31 positioned between the outer edge of the upper surface 3 and the outer edge of the rake face 32 is appropriately set according to the cutting conditions, but is set in the range of 0.05 to 0.5 mm, for example.

The rake face 32 is continuous with the land face 31 and is provided in a region closer to the central axis X than the land face 31. The rake face 32 is a face on which chips cut by the main cutting edge 6 are rubbed. Therefore, the chips of the work material 200 flow along the surface of the rake face 32. The rake face 32 is an inclined surface whose height decreases toward the center of the upper surface 3 in order to improve chip disposal.

Although not particularly illustrated, the inclination angle indicated by the angle formed between the lower surface 2 and the rake face 32 in the cross section perpendicular to the rake face 32 may be set in the range of 5 ° to 30 °, for example. The rake face 32 only needs to have a height that decreases toward the center so that chips can be scooped. Therefore, the rake face 32 may be constituted by a plurality of regions having different inclination angles.

Specifically, in the insert 1 of the present embodiment, the rake face 32 includes a first rake face 321 positioned along the curved portion 61 (first portion 61) of the main cutting edge 6, and the main cutting edge 6. It has the 2nd rake face 322 located along the straight part 62 (2nd site | part 62), and the 3rd rake face 323 located along the corner cutting edge 5. FIG. In the present embodiment, the rake angle of the second rake face 322 is larger than the rake angles of the first rake face 321 and the third rake face 323. In other words, the rake angle of the second rake face 322 is smaller than the second rake angle 322 of the first rake face 321 and the third rake face 323.

In the region of the rake face along the corner cutting edge 5 and the curved portion 62, which is a curved region in the cutting blade, the direction in which the chips flow varies in each region. Therefore, a relatively large load is likely to be applied to these rake face regions. However, since the rake angles of the first rake face 321 and the third rake face 323 are relatively large, the strength of these regions can be increased. Therefore, the durability of the insert 1 can be improved.

In the present embodiment, the rake angle of the first rake face 321 is further larger than the rake angle of the third rake face 323. Since the curvature of the corner cutting edge 5 is larger than the curvature of the curved portion 61, the change in the direction of flow of the chips flowing through the third rake face 323 is larger than the change in the direction of flow of the chips flowing through the first rake face 321. At this time, since the strength of the third rake face 323 can be increased by the relatively small rake angle of the third rake face 323, the durability of the insert 1 can be further improved.

The first rake angle 321, the second rake angle 322, and the third rake angle 333 may be evaluated by the rake angle in a cross section that passes through the center of the corresponding cutting edge region and is orthogonal to the cutting edge. For example, a rake angle in a cross section that passes through the center of the curved portion 61 and is orthogonal to the curved portion 61 at this center is the first rake face 321.

The side surface 4 is provided between the lower surface 2 and the upper surface 3. The side surface 4 functions as a flank and is connected to the outer edge of the upper surface 3. The side surface 4 has a flat portion 41 located at a location corresponding to the main cutting edge 6 and a curved surface 42 located at a location corresponding to the corner cutting edge 5. As described above, the side surface 4 has the flat portion 41 continuous with the main cutting edge 6. The length of the flat portion 41 along the direction parallel to the lower surface 2 when viewed from the side is set in a range of 5 to 20 mm, for example. The flat portion 41 is set to have a vertical length of 2 to 8 mm when viewed from the side. Moreover, the curved surface 42 is located in the location which connects the plane parts 41 located in a different side surface.

Since the flat portion 41 is provided on the side surface 4, in order to measure the wear state of the flank, it is only necessary to check how much the surface of the flat portion 41 is worn. Therefore, it becomes easy to measure wear by actually measuring from a photograph or the like. In addition, in this embodiment, although all from the upper end in the location corresponding to the main cutting edge 6 of the side surface 4 to the lower end was made into the plane part 41, it is not restricted to this. For example, a part of the portion that is continuous with the main cutting edge 6 may be a flat portion 41, and a step or the like may be provided below the flat portion 41. A main cutting edge 6 is formed at the side of the intersection of the upper surface 3 and the side surface 4. As shown in FIG. 3, the main cutting edge 6 has a concave shape as a whole when viewed from the side.

If the side surface 4 is provided with the flat surface portion 41 and the side surface 4 has the same shape of the flat surface portion 41, a plurality of types of inserts 1 can be attached to the holder without changing the shape of the holder itself. Can do. As a result, the workpiece 200 can be processed into a desired shape simply by selecting the required insert 1 and attaching it to the holder 101 according to the material of the workpiece 200 and the size of the workpiece 200. That is, it is not necessary to replace the holder 101 itself with an object corresponding to the insert 1, the manufacturing method of the cut workpiece can be simplified, and the productivity of the cut workpiece can be improved.

A main cutting edge 6 is formed at the intersection of the upper surface 3 and the side surface 4. As shown in FIG. 3, the main cutting edge 6 has a pair of first portions 61 (curved portions 61) that are concavely concaved downward when viewed from the side, and a pair of curved portions 61. It has the 2nd site | part 62 (straight part 62).

As shown in FIG. 3, the curved portion 61 is provided at a location where the height position is relatively low in the main cutting edge 6. And the corner cutting edge 5 is provided in the location where a height position is relatively high. In the vertical direction, the curved portion 61 is set to be lower than the corner cutting edge 5 in a range of 0.2 to 2 mm. The curved portion 61 is curved when viewed from the side, and has a bottom portion 6p located at the lowest position in the main cutting edge 6 in the vertical direction.

By providing the main cutting edge 6 with a curved portion 61 and a pair of straight portions 62 with the curved portion 61 interposed therebetween, the entire length of the main cutting edge 6 simultaneously contacts the work material 200 when the work material 200 is cut. There is no thing, and the part which contacts simultaneously among the full length of the main cutting blade 6 can be shortened. Specifically, one of the pair of first corner cutting edges 5 a comes into contact with the work material 200, and then the linear portion 62 and the curved portion 61 come into contact with the work material 200. As a result, the cutting resistance of the main cutting edge 6 of the insert 1 is suppressed from abruptly increasing, and the impact transmitted from the work material 200 to the insert 1 is alleviated, thereby suppressing chatter vibration from occurring in the cutting tool 100. can do.

As shown in FIG. 6, the bottom portion 6p of the curved portion 61 (the first portion 61) is located above the pair of corner cutting edges 5 (5a, 5b) with the insert 1 attached to the holder 101. It is provided near the 2 corner cutting edge 5b. In other words, when cutting the workpiece 200 located below, the bottom portion 6p is a second corner cut positioned away from the work surface of the workpiece among the pair of corner cutting edges 5 (5a, 5b). Close to the blade 5b side.

When the insert 1 cuts the work material, the bottom 6p is positioned closer to the second corner cutting edge 5b, so that the insertion depth of the main cutting edge 6 as a whole with the insert 1 attached to the holder 101 is as follows. In addition, it is possible to secure a region having a small cutting angle with respect to the work material in the main cutting edge 6. Specifically, the cutting angle of the second straight part 62b connected to the second corner cutting edge 5b can be reduced.

When the cutting amount is large as in the case where the main cutting edge 6 is used up to the region close to the second corner cutting edge 5b, the cutting resistance against the main cutting edge 6 becomes very large. However, since the cutting angle of the straight part 62b connected to the second corner cutting edge 5b to which a relatively large load is easily applied is small, the cutting resistance applied to the straight part 62b can be reduced. Therefore, the cutting resistance applied to the entire main cutting edge 6 can be suppressed.

As a result, in particular, in high-feed machining with a cutting angle of 30 ° or less, chips can be thinned and heat generation of the main cutting edge 6 can be reduced. Specifically, even if the cutting becomes deep and enormous cutting resistance is applied to the insert 1 by engraving or the like, the cutting angle of the cutting blade at the position where the cutting depth is deep is small, and the chip thickness can be reduced. Since the load applied to the blade can be reduced, occurrence of chipping of the main cutting blade 6 can be suppressed. In this way, it is possible to suppress the occurrence of chipping in the main cutting edge 6.

The insert 1 according to the present embodiment has a quadrangular shape when viewed from above, and has four sides and four corners. Each side is adjacent to a pair of corners. Therefore, the insert 1 according to the present embodiment has four main cutting edges 6. A corner cutting edge 5 is provided between the main cutting edges 6 along the outer edge of the upper surface 3. Therefore, four corner cutting edges 5 are formed.

In addition, since the insert 1 of this embodiment is quadrilateral when viewed from above, four main cutting edges 6 and four corner cutting edges 5 are formed, but the present invention is not limited thereto. The number of main cutting edges 6 and corner cutting edges 5 may be three, five, or six or more, for example, depending on the polygonal shape of the insert 1 when viewed from above.

In the cutting tool 100 shown in FIG. 4 using the insert 1 of the present embodiment, one of the four main cutting edges 6 is used for cutting a work material. Here, when the main cutting edge 6 used by long-time cutting is deteriorated, the insert 1 is once removed from the holder 101, and then the insert 1 is rotated by 90 ° with respect to the central axis X and again. What is necessary is just to attach to the holder 101. Thereby, the other unused main cutting edge 6 can be used for the cutting of the workpiece 200.

In addition, the intersection part of the upper surface 3 and the side surface 4 is not a strict line shape due to the intersection of the two surfaces. When the intersection line between the upper surface 3 and the side surface 4 is sharpened at an acute angle, the durability of the main cutting edge 6 is lowered. For this reason, a portion where the upper surface 3 and the side surface 4 intersect each other may be subjected to a so-called honing process in which the surface is slightly curved.

The main cutting edge 6 does not have a linear shape as a whole when viewed from the side, but has a concave shape downward with the lower surface 2 facing down and the upper surface 3 facing up. Specifically, the main cutting edge 6 includes a curved portion 61 (first portion 61) having a concave curve shape recessed downward, and a pair of linear portions 62 (second portion 62) provided continuously with the curved portion 61. ). The pair of linear portions 62 extend from the curved portion 61 toward the pair of corner cutting edges 5. When the main cutting edge 6 has such a shape, the main cutting edge 6 is inclined to contact with the work material as compared with the case where the main cutting edge 6 has a linear shape parallel to the upper surface 3. It becomes easy to let. Therefore, since the cutting resistance when the main cutting edge 6 bites can be reduced, the work material can be cut well.

Here, of the pair of straight portions 62 (second portion 62), the one extending toward the first corner cutting edge 5a extends toward the first straight portion 62a and the second corner cutting edge 5b. Is the second linear portion 62b.

Note that the fact that the straight line portion 62 extends toward the corner cutting edge 5 is not limited to the meaning that a virtual extension line of the straight line portion 62 intersects the corner cutting edge 5, but simply a pair of corners. It means that the

cutting blades

5a and 5b extend toward the side where the

cutting blades

5a and 5b are located. For example, in FIG. 5, since the 1st corner cutting edge 5a is located in the left end, what extended toward the left side from the curve part 61 is made into the 1st linear part 62a. In FIG. 5, since the second corner cutting edge 5b is located at the right end, the second straight portion 62b extends from the curved portion 61 toward the right side.

The shape of the curved portion 61 is not particularly limited as long as it is a concave curve shape recessed downward, and can be, for example, an arc shape, an elliptical arc shape, or a parabolic shape. In the present embodiment, the curved portion 61 has an arc shape that is recessed downward. In such a case, it becomes difficult to be affected by the axial rake when the insert 1 is attached to the holder 101, and the insert 1 can be bitten by the work material stably.

Here, the case where the main cutting edge 6 is assumed to be all linearly shaped will be described. When the main cutting edge 6 of the insert 1 begins to bite into the end surface of the work material 200, strong chatter vibration is generated strongly in the insert 1. When all of the main cutting edges 6 are simply linear, depending on the angle at which the main cutting edge 6 starts to contact the work material 200, all of the main cutting edges 6 may start to contact the work material 200 simultaneously. A large impact is applied to the insert 1 to cause vibration and chatter vibration. As a result, when chatter vibration occurs, the cutting conditions cannot be increased, and therefore the machining efficiency cannot be improved.

If all of the main cutting edge 6 has a concave curved shape that is recessed downward, the main cutting edge 6 may start to contact the work material at a point, but the work material starts to bite. And since the whole length of the main cutting edge 6 becomes long compared with what all the main cutting edges 6 are linear shape, the time which a strong impact continues to apply to the insert 1 also becomes long.

The insert 1 according to the present embodiment has a first part 61 in which the main cutting edge 6 has a concave curve shape recessed downward, and a pair of second parts 62 provided continuously with the first part 61. ing. Therefore, when starting to bite, the entire main cutting edge 6 does not hit the work material 200, and the entire length of the main cutting edge 6 is a concave curve shape in which the entire main cutting edge 6 is recessed downward. Compared with the case where it did, the whole length of the main cutting edge 6 can be shortened. Therefore, the insert 1 according to the present embodiment can reduce the cutting resistance, relieve the impact, and suppress an increase in the cutting resistance when the insert 1 starts to bite the work material.

Also, when the unevenness of the surface of the work material is large, the depth of cut always varies greatly. At this time, if the entire main cutting edge 6 has a concave curve shape, the cutting angle is not constant and stable cutting cannot be performed. However, in this embodiment, the main cutting edge 6 is a straight portion. 62, and the region where the cutting angle is constant is divided into two stages, it is possible to suppress fluctuations in cutting resistance due to changes in the cutting depth.

Moreover, as shown in FIG. 6 or FIG. 7, the bottom part 6p which is a part located in the lowermost part in the curved part 61 of the main cutting edge 6 is a work material among a pair of corner cutting edges 5 (5a, 5b). It is provided near the second one corner cutting edge 5b located away from the processing surface. The bottom 6p is formed at a position lower by, for example, 0.2 to 1.2 mm below the height of the corner cutting edge 5b. As shown in FIG. 7, the main cutting edge 6 has a length of, for example, 5 mm to 25 mm along the plane direction along the lower surface 2, and the bottom portion 6p is the length of the main cutting edge 6 in the plane direction. With respect to the center position P, the second corner cutting edge 5b is shifted by, for example, 0.5 to 1.5 mm.

Further, of the pair of straight portions 62 (62a, 62b), the second straight portion 62b closer to the second corner cutting edge 5b is formed shorter than the first straight portion 62a closer to the first corner cutting edge 5a. Therefore, it is possible to ensure a large cut amount in the entire main cutting edge 6. In the state where the insert 1 is attached to the holder 101, the inclination angle of the main cutting edge 6 with respect to the parallel line L along the work surface is the inclination angle of the first straight portion 62a extending toward the corner cutting edge 5a. For example, a1 is set to 5 to 15 °, and the inclination angle a2 of the second straight portion 62b extending toward the corner cutting edge 5b is set to 3 to 13 °. The inclination angle a2 is set to be smaller than the inclination angle a1.

Furthermore, the second straight portion 62b near the second corner cutting edge 5b of the pair of straight portions 62 (62a, 62b) is shorter than the first straight portion 62a near the first corner cutting edge 5a. The contact length with which the second linear portion 62b contacts the cutting material 200 can be effectively suppressed, and an increase in cutting resistance when the second linear portion 62b begins to bite the workpiece 200 can be suppressed. Specifically, the inclination angle a2 of the second linear portion 62b with respect to the parallel line L is smaller than the inclination angle a1 of the first linear portion 62a, and the length of the second linear portion 62b is longer than the length of the first linear portion 62a. By being short, the chip thickness of the second linear portion 62b used when the cutting depth is large can be reduced, the chipping resistance can be improved, and the strength of the insert 1 itself can also be improved.

Thus, the main cutting edge 6 has a curved portion 61 having a concave curve shape recessed downward, and a pair of linear portions 62 provided continuously with the curved portion 61. For this reason, there are good points both when the main cutting edge 6 has a linear shape and when the main cutting edge 6 has a concave curve shape. Furthermore, since the bottom portion 6p of the curved portion 61 is closer to the second corner cutting edge 5b, the contact length when contacting the work material 200 when the main cutting edge 6 is entirely linear. The disadvantage that it becomes longer can be effectively suppressed. On the other hand, since the insert 1 according to this embodiment has a shape in which the main cutting edge 6 is recessed downward as a whole, when the main cutting edge 6 comes into contact with the work material, the whole main cutting edge 6 may be in contact with the work piece at the same time. It can be avoided and good cutting can be performed.

In the insert 1 according to this embodiment, the main cutting edge 6 has a concave curved portion 61 and a pair of corner cutting blades 5 (5a, 5b) extending from the curved portion 61 to the respective corner cutting edges 5 in a side view. The bottom portion 6p of the curved portion 61 having the straight portion 62 (62a, 62b) is located above the pair of corner cutting edges 5 (5a, 5b) when cutting the workpiece 200 located below. By approaching the second corner cutting edge 5b side, the impact can be alleviated and an increase in cutting resistance when the insert 1 begins to bite into the work material 200 can be suppressed.

Further, the main cutting edge 6 in the present embodiment has a concave shape that is recessed toward the inside of the upper surface 3 when viewed from above. In other words, the main cutting edge 6 in the present embodiment has a concave shape that is recessed toward the center of the upper surface 3. Here, being recessed toward the center of the upper surface 3 means being positioned closer to the center of the upper surface 3 than a tangent line that contacts both of the pair of corner cutting edges 5 (5a, 5b). is doing. The distance between the portion closest to the center of the upper surface 3 and the tangent line is set in the range of 0.02 to 0.2 mm.

Since the main cutting edge 6 in the present embodiment has a concave shape when viewed in plan as described above, the outer periphery of the main cutting edge 6 when the insert 1 is attached to the holder 101 and the work material is cut. The cut angle on the side can be reduced. Thereby, the thickness of the chip | tip in the vicinity of the corner cutting edge 5 can be made thin at the time of shoulder processing, and the impact at the time of cutting can be relieved. Therefore, the chipping resistance of the corner cutting edge 5 and the main cutting edge 6 can be improved.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

<Cutting tools>
Next, a cutting tool 100 according to an embodiment will be described with reference to FIGS. 4 to 6 show a state in which the insert 1 is attached to an insert pocket 102 (hereinafter also simply referred to as a pocket 102) of the holder 101 with a screw 103. FIG. A two-dot chain line in FIG. 4 indicates the rotation center axis Y of the cutting tool 100.

As shown in FIGS. 4 to 6, the cutting tool 100 of this embodiment has a rotation center axis Y, a holder 101 having a plurality of pockets 102 on the outer peripheral surface on the front end side, and the above-mentioned attachments to the pockets 102, respectively. The insert 1 is provided.

The holder 101 has a substantially cylindrical shape with the rotation center axis Y as the center. A plurality of pockets 102 are provided on the outer peripheral surface on the tip side of the holder 101. The pocket 102 is a portion to which the insert 1 is mounted, and is open on the outer peripheral surface and the front end surface of the holder 101. The plurality of pockets 102 may be provided at regular intervals or at irregular intervals. Since the holder 101 is formed with a plurality of pockets 102, it is not a strict columnar shape.

Then, the insert 1 is mounted in a plurality of pockets 102 provided in the holder 101. The plurality of inserts 1 are mounted such that the main cutting edge 6 projects forward from the front end surface of the holder 101, that is, from the front end surface of the holder 101 toward the work material. Specifically, the plurality of inserts 1 are mounted on the holder 101 such that a part of the first corner cutting edge 5 a and the main cutting edge 6 protrude from the tip end surface of the holder 101.

At this time, the first corner cutting edge 5a is fixed at a position that protrudes most from the tip surface of the holder 101 during cutting. As shown in FIG. 5, the insert 1 is mounted in the pocket 102 of the holder 101 so that the corner cutting edge 5 a protrudes forward from the tip surface of the holder 101. Thereby, the bottom portion 6p of the curved portion 61 is attached to the holder 101 so as to approach the second corner cutting edge 5b located away from the processing surface of the work material.

In the present embodiment, the insert 1 is attached to the pocket 102 by the screw 103. That is, the screw 103 is inserted into the through hole H of the insert 1, the tip of the screw 103 is inserted into a screw hole (not shown) formed in the pocket 102, and the screw 103 is fixed to the screw hole. 1 is attached to the holder 101. As the holder 101, steel, cast iron, or the like can be used. In particular, it is preferable to use steel having high toughness among these materials.

<Manufacturing method of cut product>
Next, a method for manufacturing a cut product according to an embodiment will be described with reference to FIGS. 8 to 10 show a method for manufacturing a cut product. The cut workpiece is produced by cutting a work material. The cutting method in the present embodiment includes the following steps. That is,
(1) rotating the cutting tool 100 represented by the above embodiment;
(2) a step of bringing the main cutting edge 6 in the rotating cutting tool 100 into contact with the work material 200;
(3) a step of separating the cutting tool 100 from the work material 200;
It has.

More specifically, first, the cutting tool 100 is relatively moved closer to the work material 200 while being rotated around the rotation center axis Y. Next, as shown in FIG. 9, the main cutting edge 6 of the cutting tool 100 is brought into contact with the work material 200 to cut the work material 200. Then, as shown in FIG. 10, the cutting tool 100 is relatively moved away from the work material 200.

In the present embodiment, the work material 200 is fixed and the cutting tool 100 is brought closer. 8 and 9, the work material 200 is fixed and the cutting tool 100 is rotated about the rotation center axis Y. In FIG. 10, the work material 200 is fixed and the cutting tool 100 is moved away. In the cutting process in the manufacturing method according to the present embodiment, the work material 200 is fixed and the cutting tool 100 is moved in each process, but it is naturally not limited to such a form.

For example, the work material 200 may be brought close to the cutting tool 100 in the step (1). Similarly, in the step (3), the work material 200 may be moved away from the cutting tool 100. In the case of continuing the cutting process, the state in which the cutting tool 100 is rotated and the main cutting edge 6 of the insert 1 is brought into contact with a different part of the work material 200 may be repeated. When the main cutting edge 6 being used is worn, the insert 1 may be rotated 90 degrees with respect to the central axis X of the through hole H, and the unused main cutting edge 6 may be used. Note that typical examples of the material of the work material 200 include carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metal.

1 Cutting insert (insert)
2 bottom face 3 top face 31 land face 32 rake face 321 first rake face 322 second rake face 323 third rake face 4 side face 41 flat part 42 curved face 5 corner cutting edge 5a first corner cutting edge 5b second corner cutting edge 6 Main cutting edge 61 1st part (curved part)
62 Second part (straight line part)
62a First straight part 62b Second straight part 6p Bottom X Center axis H Through hole 100 Cutting tool 101 Holder 102 Insert pocket (pocket)
103 Screw Y Rotation center axis 200 Work material

Claims

A polygonal top surface having a pair of corners and a side located between the pair of corners;
A polygonal lower surface corresponding to the upper surface;
A side surface provided between the lower surface and the upper surface;
A pair of corner cutting edges located at the intersection of the pair of corners and the side surface on the upper surface;
A main cutting edge located at the intersection of the side and the side surface on the upper surface;
The main cutting edge has a concave shape recessed downward as a whole,
As viewed from the side, a concave-curved first part recessed downward;
A pair of linear second parts extending from the first part toward each of the pair of corner cutting edges and having a height increasing as approaching the pair of corner cutting edges;
The cutting insert according to claim 1, wherein a portion of the first portion located at the lowermost side is close to one of the corner cutting edges in a side view.
The cutting insert according to claim 1,
The pair of linear second portions are:
A first straight portion extending from the first portion toward one of the corner cutting edges;
A second linear portion extending from the first part toward the other corner cutting edge,
The cutting insert, wherein the first straight portion is longer than the second straight portion.
The cutting insert according to claim 1 or 2,
The said side surface has a plane part located in the location corresponding to the said main cutting blade, The cutting insert characterized by the above-mentioned.
The cutting insert according to any one of claims 1 to 3,
The cutting insert according to claim 1, wherein the main cutting edge has a concave shape recessed inward when viewed from above.
The cutting insert according to any one of claims 1 to 4,
The upper surface is
A first rake face located along the first portion of the main cutting edge;
A second rake face located along the second part of the main cutting edge;
A third rake face located along the corner cutting edge;
A cutting insert, wherein a rake angle of the second rake face is larger than a rake angle of the first rake face and the third rake face.
The cutting insert according to claim 5,
A cutting insert, wherein a rake angle of the first rake face is larger than a rake angle of the third rake face.
The cutting insert according to any one of claims 1 to 6,
The bottom of the first part is close to one of the corner cutting edges that is located away from the processing surface of the work material when cutting the work material among the pair of corner cutting edges. Cutting insert characterized by.
A holder having a plurality of insert pockets at the tip,
The cutting tool according to any one of claims 1 to 7, wherein the main cutting edge projects from the holder and is mounted in the insert pocket.
Rotating the cutting tool according to claim 8;
A step of bringing the main cutting edge in the rotating cutting tool into contact with a work material;
And a step of separating the cutting tool from the work material.